The invention relates to a bicycle seat wherein the characteristics of the seat are compatible with the anatomical characteristics of a pelvis of a bicycle rider.
A conventional bicycle seat usually comprises a broad saddle portion at a rearward region and a horn extending forward, which provides lateral support for the rider. The horn creates a pressure point at the crotch of the rider, which may adversely affect blood vessels and nerves and cause distress or injury to surrounding anatomical organs and tissues. For example, in the case of male bicycle riders, injury to the prostrate or surrounding nerves and blood vessels may occur after repeated use of the bicycle seat. Lateral support provided by such conventional bicycle seats also presents a concern for a rider because of the possibility of abrasion of soft tissue due to contact between the seat horn and the inside of the thigh.
A conventional bicycle seat is designed to provide a three-point contact for supporting the bicycle rider. The first support point is the horn itself, as mentioned above. The right ischium and the left ischium of the pelvis of the rider, which are supported on the broad saddle portion of the seat, provide two additional support points. The forces transmitted to the pelvis by the bike seat through each ischium is a source of discomfort. Further, because the upper body center-of-gravity is not necessarily centered between the ischia and the crotch contact with the horn, a force couple is created, which can cause tipping of the pelvis structure of the rider. The force couple is transferred to the sacrum, a group of fused vertebrae. A group of sacroiliac muscles join the spinal column, including the sacrum, to the pelvis. The force couple created by the bicycle seat thus has a potential for causing back pain after continued use of the bicycle seat.
Earlier prior art designs have attempted to match the design of the bicycle seat to the anatomy of a human pelvis. An example of such a design is shown in U.S. Pat. No. 591,330. That design does not provide, however, stabilizing force reactions necessary for stability of the rider. Neither does it take into account variations in the dimensions of the pelvis for different bicycle riders. Nor does it eliminate the pressure point in the region of the gluteus maximus at the end of each ischium.
U.S. Pat. No. 608,089, which is another example of prior art designs that take into account the anatomy of the bicycle rider, discloses a pair of independent saddles that are shaped to conform to the rider""s body. There is no discussion in the ""089 patent, however, of the need to eliminate pressure points. Further, the individual spring supports for the two sides of the bicycle saddle of the ""089 patent may produce a destabilizing effect on the rider.
U.S. Pat. No. 4,387,925 discloses another design that takes into account the anatomy of the bicycle rider. The weight of the rider, however, would be uniformly distributed over the entire surface of a seat of that design. This would create, as mentioned previously, pressure points as forces are transmitted to the end of each ischium.
Aside from the foregoing characteristics of prior art designs, none of those designs provides a solution to the problem of irritation of hemorrhoid tissues.
It is an objective of the invention to provide a bicycle seat that is compatible with the anatomy of a bicycle rider, whereby forces at pressure points on the pelvis structure of the rider are substantially reduced, and wherein gravity and inertia forces transmitted through the pelvis to the vehicle seat are accommodated without creating unbalanced force couples that would produce undesirable stress on the anatomy of the rider.
Accordingly, it is a further objective to provide a bicycle seat for accommodating inertia forces and gravity forces transmitted between the pelvis of the rider and the bicycle seat so that lateral stability in each lateral direction, as well as fore-and-aft stability of the rider, is accomplished.
It is an objective also to provide a bicycle seat wherein the forces transmitted between the pelvis of the rider and the seat are balanced, thereby relieving stress on the sacrum portion of the spine of the rider.
In carrying out the foregoing objectives, the invention comprises a rigid base plate on which a rider supporting cushion is affixed, the cushion having a rounded periphery. A rearward shoulder is formed on the cushion periphery to provide fore-and-aft stability.
A pair of extension plates is connected pivotally to the base plate at laterally spaced locations on opposite sides of the base plate geometric center plane. A rounded cushion is attached to each extension plate. Each extension plate is adjustable as shown by the arcuate arrows 36xe2x80x2 and 38xe2x80x2 in FIG. 3. Each rounded cushion on the extension plates registers with the rounded periphery of the base plate cushion to define a crease in a plane obliquely situated relative to the center plane of the base plate. The right ischium and the left ischium of a rider, during use of the seat by a rider, are disposed within the creases whereby gravity and inertia force components are transmitted to the rider""s pelvis in both a fore-and-aft direction and in each lateral direction. This provides transverse and fore-and-aft stability. The fore-and-aft stability provided by the rearward shoulder on the base plate cushion complements the stability provided by the extension plate cushions.
The ischium is the lowest and the strongest portion of the pelvis bone. It extends downward to form a large tuberosity. It then curves forward to form the pubis. The ischium also forms the lower and back part of the hip bone.
A female pelvis is less massive than a male pelvis, and the ilia of a female pelvis are less curved so that the iliac spines of the lower portion of the ischia are more widely separated. These differences between the male pelvis and the female pelvis make it necessary to adjust the lateral distance between the extension plates so that the seat assembly can accommodate both female and male riders with maximum stability and comfort. The adjustment of the extension plates relative to the base plate is accommodated in the design of the invention by a pivotal connection between the two extension plates and the base plate.
The base plate is supported by a rail holder support at the underside of the base plate. A pair of fore-and-aft adjustment support rails is secured to the rail holder, which in turn is secured to the underside of the base plate. An adjustable lock mechanism permits the seat assembly to be adjusted in a fore-and-aft direction along the support rails so that the position of the seat can be adjusted to suit the preference of the rider.